The purpose of this study is to determine whether ivacaftor, a recently FDA-approved CFTR potentiator, improves bone micro-architecture and strength in patients with cystic fibrosis with at least one G551D CFTR mutation.

Subjects with CF ages 6 to 75 years old who will be or have started taking ivacaftor within the previous 6 months

Subjects with CF not taking ivacaftor

Subjects with CF ages 6 to 75 years old who will not be taking ivacaftor, matched for age, race, and gender with cohort 1

Healthy subjects

Healthy subjects with no medical conditions known to affect bone between the ages of 6 to 75 years old, matched for age, race, and gender with cohort 2.

Detailed Description:

Ivacaftor, a CFTR potentiator, has recently been FDA approved for the treatment of cystic fibrosis in patients with at least one G551D CFTR mutation. Given the possible role of CFTR in bone, we hypothesize that this medication may also improve bone health in CF patients. The purpose of this study is to test this hypothesis using high resolution peripheral quantitative computed tomography, a research tool that measures bone micro-architecture and volumetric bone density and has the ability to detect small changes in bone that might otherwise be missed with standard bone imaging techniques such as bone density testing.

Eligibility

Ages Eligible for Study:

6 Years to 75 Years

Genders Eligible for Study:

Both

Accepts Healthy Volunteers:

Yes

Sampling Method:

Non-Probability Sample

Study Population

Subjects with CF will be recruited from the Cystic Fibrosis Centers at Children's Hospital Boston and Massachusetts General Hospital. Healthy subjects will be a community sample recruited from nearby communities.

Criteria

COHORT 1

Inclusion Criteria:

Age 6 to 75 years old

Established diagnosis of CF with at least one abnormal G551D-CFTR allele

Eligibility for and intent to start treatment with ivacaftor or started treatment with ivacaftor within previous 6 months

Exclusion Criteria:

Psychiatric or mental incapacity that would preclude subject from assenting to study participation

Current pregnancy

History of organ transplantation

History of Burkholderia dolosa infection

COHORT 2:

Subjects will be grouped by gender, age and race to match subjects in Cohort 1 within two years. Pubertal subjects will be matched by Tanner stage.

Inclusion Criteria:

Age 6 to 75 years old

Established diagnosis of CF

Exclusion Criteria:

Psychiatric or mental incapacity that would preclude subject from assenting to study participation

Current pregnancy

History of organ transplantation

History of Burkholderia dolosa infection

COHORT 3:

Subjects will be grouped by gender, age and race to match subjects in Cohort 2 within two years. Pubertal subjects will be matched by Tanner stage.

Inclusion criteria:

Age 6 to 75 years old

Clinically stable, deemed able to complete the screening, baseline, and scheduled study visits.

Exclusion criteria:

History of significant cardiac, renal, pulmonary, hepatic, or malignant disease, current alcohol or illicit drug abuse, or major psychiatric disorder

History of a non-digital fracture in the previous 6 months, history of one pathologic fracture, or greater than four total lifetime non-digital fractures

Cumulative lifetime use of oral glucocorticoids for greater than 2 months

Current or prior use of medications known to affect bone metabolism including hormone replacement therapy, anti-estrogens, bisphosphonates, calcitonin, fluoride, lithium, suppressive doses of levothyroxine, or anticonvulsants.

Pregnancy

BMI less than 18.5 or greater than 30 kg/m2 in subjects 18 years and older, or BMI less than 5th or greater than 95th percentile in subjects under the age of 18 years.

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Please refer to this study by its ClinicalTrials.gov identifier: NCT01549314